Load dynamic cpu lib on windows

On linux, we link the CPU library in to the Go app and fall back to it
when no GPU match is found. On windows we do not link in the CPU library
so that we can better control our dependencies for the CLI.  This fixes
the logic so we correctly fallback to the dynamic CPU library
on windows.

llm/ext_server_windows.go

@@ -1,8 +1,6 @@
 package llm
 
 import (
-	"fmt"
-
 	"github.com/jmorganca/ollama/api"
 )
 
@@ -10,6 +8,5 @@ func newDefaultExtServer(model string, adapters, projectors []string, numLayers
 	// On windows we always load the llama.cpp libraries dynamically to avoid startup DLL dependencies
 	// This ensures we can update the PATH at runtime to get everything loaded
 
-	// Should not happen
+	return newDynamicShimExtServer(AvailableShims["cpu"], model, adapters, projectors, numLayers, opts)
-	return nil, fmt.Errorf("no default impl on windows - all dynamic")
 }

llm/llama.cpp/gen_windows.ps1

@@ -49,6 +49,9 @@ function install {
     md "${script:buildDir}/lib" -ea 0 > $null
     cp "${script:buildDir}/bin/${script:config}/ext_server_shared.dll" "${script:buildDir}/lib"
     cp "${script:buildDir}/bin/${script:config}/llama.dll" "${script:buildDir}/lib"
+
+    # Display the dll dependencies in the build log
+    dumpbin /dependents "${script:buildDir}/bin/${script:config}/ext_server_shared.dll" | select-string ".dll"
 }
 
 function cleanup {

llm/llm.go

@@ -87,7 +87,8 @@ func newLlmServer(library, model string, adapters, projectors []string, numLayer
 		if err == nil {
 			return srv, nil
 		}
-		log.Printf("Failed to load dynamic library - falling back to CPU mode %s", err)
+		log.Printf("Failed to load dynamic library %s - falling back to CPU mode %s", library, err)
+		// TODO - update some state to indicate we were unable to load the GPU library for future "info" ux
 	}
 
 	return newDefaultExtServer(model, adapters, projectors, numLayers, opts)

llm/shim_ext_server_windows.go

@@ -4,6 +4,7 @@ import (
 	"embed"
 	"log"
 	"os"
+	"path/filepath"
 	"strings"
 )
 
@@ -11,14 +12,20 @@ import (
 var libEmbed embed.FS
 
 func updatePath(dir string) {
+	tmpDir := filepath.Dir(dir)
 	pathComponents := strings.Split(os.Getenv("PATH"), ";")
+	i := 0
 	for _, comp := range pathComponents {
-		// Case incensitive
+		if strings.EqualFold(comp, dir) {
-		if strings.ToLower(comp) == strings.ToLower(dir) {
 			return
 		}
+		// Remove any other prior paths to our temp dir
+		if !strings.HasPrefix(strings.ToLower(comp), strings.ToLower(tmpDir)) {
+			pathComponents[i] = comp
+			i++
+		}
 	}
-	newPath := strings.Join(append(pathComponents, dir), ";")
+	newPath := strings.Join(append([]string{dir}, pathComponents...), ";")
 	log.Printf("Updating PATH to %s", newPath)
 	os.Setenv("PATH", newPath)
 }